1. Technical Field
The present invention relates to an inflator for a vehicle occupant protection device. In particular, the present invention relates to an inflator that includes (a) an autoignition mechanism and/or (b) a mechanism for the deactivation of the second stage of a dual stage air bag inflator.
2. Description of the Prior Art
An inflator for an inflatable vehicle occupant protection device, such as an air bag, includes a source of inflation fluid. Some known inflators include an autoignition device or mechanism. The autoignition device is operable to actuate the inflation fluid source when the temperature of the inflator reaches a predetermined temperature. Such actuation can avoid having the inflator actuated at a higher temperature experienced, for example, in a vehicle fire when the inflator housing has gotten so hot that the housing material has weakened.
Some inflators are of the xe2x80x9cdual stagexe2x80x9d type and include two separate, independently actuatable inflation fluid sources (xe2x80x9cstagesxe2x80x9d). The two inflation fluid sources can be actuated simultaneously or at different times to tailor the rate and volume of flow of inflation fluid out of the inflator. In some cases, only one of the inflation fluid sources is actuated, for example, when a relatively low fluid flow rate is desired. In these cases, the second inflation fluid source remains active after deployment of the air bag. It may be desirable, for safety reasons, to deactivate the second inflation fluid source when it has not been used to inflate the air bag.
The present invention is an apparatus for inflating an inflatable vehicle occupant protection device. The apparatus comprises a housing and an inflation fluid source in the housing for, when actuated, providing gas for inflating the protection device. The apparatus also comprises an electrically actuatable initiator connected with the housing for actuating the inflation fluid source. The apparatus further comprises vehicle electric circuitry for actuating the initiator to actuate the inflation fluid source in response to sensing an occupant protection event for which inflation of the protection device is desired. A microelectromechanical system device (MEMS device) in the apparatus is electrically energizable to cause actuation of the inflation fluid source. Means responsive to an event other than an occupant protection event energizes the MEMS device to cause actuation of the inflation fluid source.
In one embodiment, the means responsive to an event other than an occupant protection event comprises means responsive to an increase in temperature in the housing above a predetermined temperature.
In another embodiment, the inflation fluid source comprises a primary inflation fluid source and a secondary inflation fluid source actuatable independently of each other. The means responsive to an event other than an occupant protection event comprises means responsive to sensing of lapse of a predetermined period of time after actuation of only the primary inflation fluid source.